CNS tumours and ICP

Question 1

In which region of the cranium do childhood tumors arise?
How would it present?

Answer 1

Posterior fossa
Enlarged head and hydrocephalus in children

Question 2

In which region of the cranium do adult tumors arise?

Answer 2

Cerebral hemispheres- supratentorial

Question 3

Discuss the local spread of CNS tumors.

Answer 3

May infiltrate the dura, skull, sinuses
Tumours are able to spread through the CSF implantation along the brain and spinal cord at a distance from the original tumour site (seeding)

Question 4

Discuss meningiomas.

Answer 4

Benign
Usually dura
from meningothelial cells of the arachnoid

Gross:
Rounded masses with well-defined
Dural bases that compress the underlying brain
Extension into the overlying bone may be present

Question 5

Discuss the Astrocytomas:Pilocytic astrocytomas (grade I).

Answer 5

Common childhood
cerebellum, but also the floor of walls of the third ventricle, optic nerves, and occasionally cerebral hemisphere

Often cystic with a mural nodule

Question 6

Discuss the Astrocytomas: Diffuse astrocytoma (grade 2)

Answer 6

young adults mid-30s

Tumour is poorly defined, gray, infiltrative, expands and distorts the invaded brain
Firm or soft and gelatinous; cystic degeneration may be seen

Question 7

Discuss the Astrocytomas: Anaplastic astrocytoma (grade 3).

Answer 7

4th decade
cortex and white matter, frontal lobe

Typically invade the surrounding brain without overt tissue destruction
Mass-like appearance on cut section

Question 8

Discuss the Astrocytomas: Glioblastoma (grade 4).

Answer 8

Frequent in adults
cerebral hemispheres
High grade
die in 6 months

Poorly defined mass with necrosis and haemorrhage

Question 9

Discuss Oligodendrogliomas (grade 2)

Answer 9

4th and 5th decades
cerebral hemispheres and prediction for white matter.

Well-circumscribed, gelatinous, gray masses
Often with cysts, focal hemorrhage, and calcification

Question 10

Discuss Ependymomas (grade 2).

Answer 10

arise next to the ependyma-lined ventricular system and central canal of the spinal cord.
Occurs in children and adults
May seed along the CSF pathway down the spinal cord
Slow-growing tumors and the prognosis is usually good

Well-demarcated, solid or papillary mass arising from the floor of the ventricle

Question 11

Discuss medulloblastoma.

Answer 11

Children-cerebellum
aggressive
local infiltration
sensitive to radiotherapy

Question 12

Discuss Choroid plexus tumours.

Answer 12

Papillomas and carcinomas
papillary and intraventricular.
hydrocephalus and seeding via the CSF pathway

Question 13

Discuss Primary lymphomas of the brain.

Answer 13

immunosuppressed, AIDS
high grade
Diffusely infiltrative

Question 14

From which site can tumours metastasize to the brain?

Answer 14

Most common primary sites are:
Lung
Breast
Skin (melanoma)
Kidney
Gastrointestinal tract

RARE: choriocarcinoma, but has a high likelihood of metastasizing to the brain

Question 15

How does cranial pressure usually increase?

Answer 15

generalized cerebral oedema
increased CSF volume (hydrocephalus)
Focally expanding mass lesions

Question 16

Outline the clinical features of the increased ICP.

Answer 16

Oedema of the optic papilla (papilloedema) with blurred vision
Nausea and vomiting due to pressure on the pons and medulla (vomiting centre)
Headache due to distension of the dura
Neck stiffness due to pressure around the cerebellar cones
Impaired consciousness
Ininfants: macrocephaly, bulging fontanelle, sunset sign
Increased pressure gradient within theskullin the presence of inflexible brain structures (e.g.Tentorium cerebelli) → flexible brain tissueshifts→ possiblebrain tissueherniation
Cushing triad: ): irregular breathing, elevated systolic BPandbradycardia

Question 17

Discuss the Cushing triad.

Answer 17

(if brainstem is compressed): irregular breathing, elevated systolic BPandbradycardia
↑ Intracranialpressure→↓ perfusionpressure within the brain → compensatory activation of thesympathetic nervous systemto maintain cerebral perfusion →↑systolicblood pressure→ stimulation ofaortic archbaroreceptors→ activation of theparasympathetic nervous system(vagus) →bradycardia
↑ Pressureonbrainstem→dysfunction ofrespiratory center→ irregular breathing

Question 18

Outline the pathways of oedema formation in the brain.

Answer 18

Vasogenic oedema: increase in extracellular fluid due to increased vascular permeability.
Cytotoxic oedema: increase in intracellular fluid (cell swelling) secondary to neuronal, glial, or endothelial cell membrane injury
Interstitial oedema (hydrocephalic oedema) occurs when an increase in intravascular pressure causes an abnormal flow of fluid from the intraventricular CSF across the ependymal lining to the periventricular white matter.

Question 19

Describe the gross appearance cerebral oedema.

Answer 19

Gyri are flattened and widened
Intervening sulci are narrowed
Ventricular cavities are compressed

Question 20

What are the causes of hydrocephalus?

Answer 20

Obstructive: obstruction to CSF outflow - commonest
Excess production: seen with choroid plexus tumours
Decreased reabsorption: Rare

Question 21

Describe the effect of hydrocephalus in infants.

Answer 21

An increased volume of CSF within the ventricles expands them and can increase the intracranial pressure.
When hydrocephalus develops in infancy before closure of the cranial sutures, there is enlargement of the head  increased head circumference (macrocephaly)
Hydrocephalus developing after this period is associated with expansion of the ventricles and increased intracranial pressure, without a change in head circumference

Question 22

Define non-communicating hydrocephalus.

Answer 22

obstructive hydrocephalus: ventricular system is obstructed and does not communicate with the subarachnoid space, as may occur because of a mass in the third ventricle

Question 23

Define communicating hydrocephalus.

Answer 23

the ventricular system is in communication with the subarachnoid space, and there is enlargement of the entire ventricular system.

Question 24

Define Hydrocephalus ex vacuo.

Answer 24

compensatory increase in ventricular volume secondary to a loss of brain parenchyma.

Question 25

Define cerebral herniation.

Answer 25

Displacement of brain tissue past rigid dural folds (the falx and tentorium) or through openings in the skull because of increased intracranial pressure.

Question 26

Discuss subfalcine herniation.

Answer 26

cingulate gyrusof one hemisphere is compressed and herniates under thefalx cerebri→compression of:
Contralateralhemisphere→ obstruction of theforamen of Monro→hydrocephalus
Pericallosal arteries→hemiparesis(predominantly lower limbs)

Question 27

Discuss uncal herniation.

Answer 27

medialtemporal lobe(the uncus) herniates at the tentorial incisure
→Compression of:
Ipsilateraloculomotor nerve palsy→fixed and dilated pupil
Ipsilateralposterior cerebral artery→cortical blindnesswithcontralateralhomonymous hemianopia
Contralateralcerebral peduncle →ipsilateralparalysis +Kernohan’s phenomenon(a syndrome ofuncal herniationcharacterized by pupillary dilationipsilateralto theherniation, due toCN IIIcompression) and, paradoxically,ipsilateralweakness (due tocontralateralcerebral peduncle compression). This is unusual because commonly, anipsilateralbrain lesion results incontralateralmotor symptoms. It occurs in patients withincreased ICPcaused by intracranial hemorrhage orcerebral edema.)
→Downward shift of thebrainstem→brainstemhemorrhages → focal deficits, impaired consciousness, death

Question 28

Discuss foramen magnum herniation.

Answer 28

structures of theposteriorfossa (e.g.,cerebellar tonsils, medulla) herniate at theforamen magnum→ impaired consciousness, decerebrate posturing,apnea, impaired circulation, death

Question 29

What is the medical therapy for Increased ICP?

Answer 29

Osmotic diuretics
IVmannitol: can generally be administered every6–8 hours, effects last for up to24 hours
IV hypertonicsaline: particularly forshort-termtreatment
Removal ofCSFvia an intraventricular monitor with drainage system (e.g., external ventricular drain) or acerebral shunt(e.g., inhydrocephaluspatients)

Question 30

Describe the pathogenesis of papilloedema.

Answer 30

Vasogenic oedema involves more severely the white matter and extends along the optic nerves and into the optic papillae (papilloedema)

The oedematous optic papillae protrude forward into the vitreous chamber and displace the retina, causing blurring of vision

Fundoscopic examination reveals blurred disk margins

Question 31

Define sunset signs.

Answer 31

Pressure on CN 3,4,6
forces eyes down
revealing a rim of sclera